Analog systems and digital systems are commonly implemented in an integrated circuit using system on-chip (SOC) technology. Such systems commonly include an analog front end (AFE) circuit. The AFE circuit operates as an interface between an external input terminal, through which analog signals are input, and a digital signal processing unit that processes the received signals in digital format.
The AFE circuit is widely used in various devices, such as down converters for wireless digital communication devices, digital image scanners, digital cameras and voice codecs, and the like. The AFE circuit includes an amplifier and an analog to digital converter (ADC). The amplifier amplifies the received analog signals, and the ADC converts the amplified analog signals into digital signals. The AFE along with the ADC has an associated offset. This offset drifts with temperature. The existing techniques provide dynamic storing of offset. However, there are inherent shortcomings of these techniques which are now described:                (a) Dynamically storing of offset requires an offset storing phase. If sampling mode of the ADC is used for storing offset, then a comparator in the ADC cannot be powered down during sampling phase. If conversion mode of the ADC is used for storing offset, it slows down the ADC.        (b) All devices in the AFE are required to store their offset individually to avoid saturation. This increases the complexity of the AFE; and/or        (c) Dynamic storing of offset results in storage of noise also. This increases a white noise of the AFE.        